The invention relates to a turnbuckle for connecting a hollow section, which is provided with a catch recess, with a carrier element having a clamping edge shoulder, and particularly for connecting hollow section rods with vertical supports, which are provided with undercut grooves as clamping edge shoulders and are intended for racks, which can be put together and taken apart, with a housing, which can be introduced into the hollow section, and locked in the catch recess of the hollow section by means of a catch and with a clamping spring, which can be converted by a rotating motion of the catch from a starting stretching position to a final stretching position and with a clamping finger part, which in the final stretching position grips behind the clamping edge shoulder, the clamping spring and the catch being disposed movably in the housing and the clamping finger part being movable in the course of the stretching motion of the clamping spring over an abutment, which can be fixed in the housing, into a stretching-spreading position, which is directed transversely to the longitudinal axis of the housing.
A turnbuckle of the aforementioned type is known from the EP-A-O 059 463. In the case of this turnbuckle, the catch is constructed as a cam, which grips through a hole-shaped recess of the housing. In the starting stretching position, the catch can be depressed by way of the clamping spring, so that, after being depressed, it can be introduced together with the housing into the interior of the hollow section. In the installed position, a hollow section recess, which overlaps the catch, is provided in the hollow section, so that the catch locks in the hollow section recess under the influence of the force of the clamping spring and ensures that the turnbuckle is connected reliably with the hollow section. In the final stretching position of the clamping spring, in which the hook-shaped end of the clamping finger part and of the clamping spring is locked over the cam of the catch behind the clamping edge shoulder of the carrier element, the catch is prevented from being impressed by a supporting element in the side of the housing. The clamping finger part or clamping spring has inclined surfaces interacting with indentations in the side of the housing in order to be able to carry out, in the course of the catch movement, a stretching-spreading motion directed transversely to the longitudinal axis of the housing. This makes greater demands on the accuracy of fit of the parts. Accordingly, the cam of the catch element has to be manufactured very precisely, in order to be able to use the cam, which is supported on only one side, with a manageable expenditure of force reliably for fastening the turnbuckle and, with that, the hollow section to the supporting element. Nevertheless, the forces, which must be employed for manually bracing this turnbuckle, are appreciable.